U.S. patent application number 10/567202 was filed with the patent office on 2006-09-07 for pvc hollow filtration membrane and the preparation method thereof.
Invention is credited to Lianggang Chen.
Application Number | 20060196825 10/567202 |
Document ID | / |
Family ID | 34121271 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060196825 |
Kind Code |
A1 |
Chen; Lianggang |
September 7, 2006 |
Pvc hollow filtration membrane and the preparation method
thereof
Abstract
The present invention provides a polyvinyl chloride hollow
filtration membrane, which mainly comprises the following
components: 30-95 wt. % of polyvinyl chloride and 5-70 wt. % of
vinyl chloride-vinyl acetate-maleic anhydride terpolymer, wherein
the polymerization degree of polyvinyl chloride is from 700 to
2500; the content of vinyl acetate is 10-19 % and the content of
maleic anhydride is 18-40 % on a basis of total weight of the
terpolymer; and the absolute viscosity of the terpolymer is 1.2-1.9
mPa.cndot.s. A method for preparing such a polyvinyl chloride
hollow filtration membrane is also provided in the present
invention.
Inventors: |
Chen; Lianggang; (Shanghai,
CN) |
Correspondence
Address: |
DORSEY & WHITNEY LLP;INTELLECTUAL PROPERTY DEPARTMENT
50 SOUTH SIXTH STREET
MINNEAPOLIS
MN
55402-1498
US
|
Family ID: |
34121271 |
Appl. No.: |
10/567202 |
Filed: |
August 2, 2004 |
PCT Filed: |
August 2, 2004 |
PCT NO: |
PCT/CN04/00887 |
371 Date: |
February 3, 2006 |
Current U.S.
Class: |
210/500.23 ;
210/500.42; 264/41 |
Current CPC
Class: |
B01D 67/0013 20130101;
B01D 69/08 20130101; B01D 71/30 20130101; B01D 2323/26 20130101;
B01D 2325/24 20130101; B01D 2323/08 20130101; B01D 2323/06
20130101; B01D 67/0011 20130101 |
Class at
Publication: |
210/500.23 ;
210/500.42; 264/041 |
International
Class: |
B01D 71/28 20060101
B01D071/28 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 6, 2003 |
CN |
03127516.8 |
Claims
1. A polyvinyl chloride hollow filtration membrane, which mainly
comprises the following components: 30-95 wt. % of polyvinyl
chloride, and 5-70 wt. % of vinyl chloride-vinyl acetate-maleic
anhydride terpolymer, wherein the polymerization degree of
polyvinyl chloride is from 700 to 2500; the content of vinyl
acetate is 10-19% and the content of maleic anhydride is 18-40% on
a basis of total weight of the terpolymer; and the absolute
viscosity of the terpolymer is 1.2-1.9 mPa.cndot.s.
2. The polyvinyl chloride hollow filtration membrane of claim 1,
wherein the content of polyvinyl chloride is 60-80 wt. %, and the
content of the terpolymer is 20-40 wt. %.
3. The polyvinyl chloride hollow filtration membrane of claim 1,
wherein the content of vinyl acetate is 13-15% and the content of
maleic anhydride is 20-28% on a basis of total weight of the vinyl
chloride-vinyl acetate-maleic anhydride terpolymer.
4. A method for preparing a polyvinyl chloride hollow filtration
membrane, which comprises the following steps: formulating a
spray-membrane slurry having the following components on a basis of
total weight of a slurry for preparing the membrane: TABLE-US-00002
polyvinyl chloride 5.6-14.1% vinyl chloride-vinyl acetate-maleic
0.4-13.0% anhydride terpolymer thermal stabilizer 0.1-0.7% organic
solvent 61.5-85.1% hole-making agent 1.1-10.4%
wherein the polymerization degree of polyvinyl chloride is from 700
to 2500; the content of vinyl acetate is 10-19% and the content of
maleic anhydride is 18-40% on a basis of total weight of the
terpolymer; and the absolute viscosity of the terpolymer is 1.2-1.9
mPa.cndot.s; mixing the polyvinyl chloride, vinyl chloride-vinyl
acetate-maleic anhydride terpolymer, heat stabilizer and organic
solvent within the above proportion ranges, dissolving the mixture
at 40-90.degree. C., then adding a hole-making agent therein,
dissolving for 10-24 hours with continuous stirring, and standing
for 10-15 hours to form the spray-membrane slurry; and spraying the
membrane by a known method to solidify the membrane, thereby
forming the polyvinyl chloride hollow filtration membrane.
5. The method of claim 4, wherein the spray-membrane slurry is
prepared at a temperature of 50-80.degree. C.
6. The method of claim 4, wherein the thermal stabilizer is one or
more selected from the group consisting of barium stearate,
organotin and a lead compound.
7. The method of claim 6, wherein the thermal stabilizer is
thiolmethyltin.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a polyvinyl chloride hollow
filtration membrane, especially to a modified polyvinyl chloride
hollow filtration membrane having good permeability and
anti-pollution properties.
BACKGROUND OF THE INVENTION
[0002] Due to the characteristics such as energy conservation,
environmental protection and easy operation of the membrane
isolation technique, the industry of membrane isolation has
developed rapidly, and the application scope thereof has been
extended to the fields such as biology, medicament, environmental
protection, energy sources, municipal water treatment, and waste
water treatment. A hollow filtration membrane, due to its large
filtration area per unit volume, low cost of the manufacture of
equipment, and the realization of cross flow filtration, makes the
life time of the filter element greatly extended. However, the
current commercialized hollow filtration membrane products
generally utilize materials such as polysulfones (PS),
polyvinylidene fluorides (PVDF), polyethersulfones (PES), and
polyacrylonitriles (PAN), which cannot be widely used due to their
low ratios of quality to price.
[0003] Polyvinyl chlorides are attracting more and more attention
from research units, as they have good physical properties and
chemical stability, are resistant to microorganism erosion, acids
and bases, and have a lot of sources and varieties, the price of
which is low. However, since the hydrophilicity of polyvinyl
chloride materials themselves is not good, polyvinyl chloride
filtration membranes have no good penetration property and are
easily polluted, thus causing the filtration property thereof to
decline rapidly.
[0004] To produce liquid separation membranes of polyvinyl chloride
having excellent properties, it is necessary to improve the
hydrophilicity thereof after the membrane is formed. To realize it,
the following methods may be employed: (1) copolymerization
modification, i.e. introducing other chemical substances having
hydrophilic groups into vinyl chloride chain segments by
copolymerization; (2) plasma surface modification, i.e. treating
polyvinyl chloride powders or membranes with plasma to produce
hydrophilic groups containing chlorine on the surfaces of polyvinyl
chloride powders or membranes; and (3) surface grafting
modification (one of filtration membrane chemical modification),
i.e. making polyvinyl chloride molecule chain produce free radicals
by high energy radiation such as Y-ray and electron beam, then
introducing the desired hydrophilic groups into the membrane
surface by graft polymerization. All of the above three methods can
realize the improvement of the hydrophilicity property of polyvinyl
chloride filtration membrane, but their industrialization is not
easy, as the cost is high.
[0005] The fourth modification method for polyvinyl chloride
filtration membrane is called as co-blend modification, i.e. adding
a co-blend material, which is compatible with polyvinyl chloride
materials and has hydrophilic groups, into a slurry for preparing
the membrane. The less the difference of solubility parameters
(representing the solubility property of a macromolecule material)
between the two materials is, then the better the compatibility of
the two materials is, the more stable the slurry for preparing the
membrane is, the more uniform the aperture of the formed membrane
is, and the less the drawbacks are. Furthermore, the better the
hydrophilicity property of the selected co-blend material is, and
the higher the ratio thereof in the slurry for preparing the
membrane is, then the higher the water flux of the membrane is, and
the better the anti-pollution property thereof is. Therefore, the
selection of proper co-blend material and the use of the proper
molding technique can produce a polyvinyl chloride hollow
filtration membrane having good mechanical properties, high water
flux and good anti-pollution property, which has a good quality and
low cost.
SUMMARY OF INVENTION
[0006] An object of the present invention is to provide a polyvinyl
chloride hollow filtration membrane having good penetration
property and remarkable anti-pollution property.
[0007] Another object of the present invention is to provide a
method for preparing a polyvinyl chloride hollow filtration
membrane.
[0008] The polyvinyl chloride hollow filtration membrane of the
present invention mainly comprises the following components: [0009]
30-95 wt. % of polyvinyl chloride, and [0010] 5-70 wt. % of vinyl
chloride-vinyl acetate-maleic anhydride terpolymer,
[0011] wherein the polymerization degree of polyvinyl chloride is
from 700 to 2500; the content of vinyl acetate is 10-19% and the
content of maleic anhydride is 18-40% on a basis of total weight of
the terpolymer; and the absolute viscosity of the terpolymer is
1.2-1.9 mPa.cndot.s.
[0012] The present invention also provides a method for preparing a
polyvinyl chloride hollow filtration membrane, which comprises the
following steps:
[0013] formulating a spray-membrane slurry having the following
components on a basis of total weight of the slurry: TABLE-US-00001
polyvinyl chloride 5.6-14.1% vinyl chloride-vinyl acetate-maleic
0.4-13.0% anhydride terpolymer thermal stabilizer 0.1-0.7% solvent
61.5-85.1% hole-making agent 1.1-10.4%
wherein the polymerization degree of polyvinyl chloride is from 700
to 2500; the content of vinyl acetate is 10-19% and the content of
maleic anhydride is 18-40% on a basis of total weight of the
terpolymer; and the absolute viscosity of the terpolymer is 1.2-1.9
mPa.cndot.s;
[0014] mixing the polyvinyl chloride, vinyl chloride-vinyl
acetate-maleic anhydride terpolymer, heat stabilizer and solvent
within the above proportion ranges, dissolving the mixture at
40-90.degree. C., then adding a hole-making agent therein,
dissolving for 10-24 hours with continuous stirring, and standing
for 10-15 hours to form the spray-membrane slurry; and
[0015] spraying the membrane by a known method to solidify the
membrane, thereby forming the polyvinyl chloride hollow filtration
membrane of the present invention.
DETAILED DESCRIPTION OF INVENTION
[0016] In the polyvinyl chloride hollow filtration membrane of the
present invention, the content of polyvinyl chloride is 30-95 wt.
%, preferably 60-80 wt. %, and the content of the vinyl
chloride-vinyl acetate-maleic anhydride terpolymer is 5-70 wt. %,
preferably 20-40 wt. %. Said filtration membrane further inevitably
contains a trace quantity of residual solvent and other
impurities.
[0017] In the vinyl chloride-vinyl acetate-maleic anhydride
terpolymer used in the present invention, the content of vinyl
acetate is 10-19 wt. %, preferably 13-15 wt. %, and the content of
maleic anhydride is 18-40 wt.%, preferably 20-28 wt. %. The
terpolymer contains a strong hydrophilic group (-COOH), which has a
water contact angle of 40 degree and a solubility parameter of
9.5-9.7 (J/cm.sup.3).sup.1/2. The solubility parameter of said
vinyl chloride-vinyl acetate-maleic anhydride terpolymer is very
close to that of the polyvinyl chloride (9.6 (J/cm.sup.3).sup.1/2),
so the compatibility of these two materials are very good, and can
be blended almost in any ratio.
[0018] In the method for preparing the membrane of the present
invention, the solvent may be selected from the group consisting of
dimethyl formamide (DMF) or dimethyl acetamide (DMAC). The thermal
stabilizer may be selected from the group consisting of barium
stearate, organotin, and a lead compound, preferably
thiolmethyltin. The main function of the stabilizer is to avoid the
thermal degradation of the polyvinyl chloride produced in the
process of formulating and heating the slurry. The hole-making
agent can increase the percentage of open area of the membrane,
enhance the penetration property of the membrane, and will be
helpful to improve the toughness thereof. The hole-making agent can
be selected from the group consisting of polyvinyl pyrrolidone
(PVP) and polyethylene glycol (PEG), preferably polyethylene glycol
(PEG). The slurry for preparing the membrane can be prepared at a
temperature of 40-90.degree. C., preferably 50-80.degree. C.
[0019] The vinyl chloride-vinyl acetate-maleic anhydride terpolymer
used in the present invention has good hydrophilicity property, and
physical and chemcial properties, and is compatible with polyvinyl
chloride, the cost of which is relatively low. The addition of the
vinyl chloride-vinyl acetate-maleic anhydride terpolymer can
greatly improve the hydrophilicity and anti-pollution properties of
the formed membrane. For example, when the weight ratio of vinyl
chloride-vinyl acetate-maleic anhydride terpolymer to polyvinyl
chloride is 3:7, the water contact angle of the filtration membrane
is 57 degree, while the water contact angle of the complete
polyvinyl chloride filtration membrane is 66 degree.
[0020] The spray-membrane slurry of the present invention can be
used to spray the membrane by a known dry jet-wet spinning method,
then be solidified in a coagulant to form a membrane, wherein the
coagulant is water or an aqueous solution containing a certain
solvent. Thus, the polyvinyl chloride hollow filtration membrane of
the present invention, which has excellent properties, is
prepared.
EXAMPLES
[0021] Now the present invention is further detailedly illustrated
in combination with the following examples. However, it is
appreciated that these examples are only intended to illustrate the
invention, but not to limit the scope of the invention.
EXAMPLE 1
[0022] A uniform spray-membrane slurry was prepared according to
the following procedure: 11.5 wt. % of polyvinyl chloride, 5.0 wt.
% of vinyl chloride-vinyl acetate-maleic anhydride terpolymer and
0.3 wt. % of thiolmethyltin stabilizer were mixed; then the
mixture, together with 76.3 wt. % of DMAC, were poured into a
stirring vessel at a temperature of 78.degree. C. with the stirring
rotation speed of 110 rpm; after they were basically dissolved, 6.9
wt. % of PEG was added therein; then they were stirred for 10 hours
at a constant temperature of 78.degree. C., the vacuum debubbling
was performed, and they were stood for 12 hours to form the
spray-membrane slurry. The resulting spray-membrane slurry was
extruded through an spinneret by a dry jet-wet spinning method,
then it was passed through a water coagulant to produce a hollow
filtration membrane. The resulting membrane has a retention
molecule weight of 80,000 daltons, and has a pure water filtration
yield of 800 L/m.sup.2h at a pressure of 0.1 MPa and a water
temperature of 25.degree. C.
EXAMPLE 2
[0023] A uniform spray-membrane slurry was prepared according to
the following procedure: 9.4 wt. % of polyvinyl chloride, 3.3 wt. %
of vinyl chloride-vinyl acetate-maleic anhydride terpolymer and 0.2
wt. % of thiolmethyltin stabilizer were mixed; then the mixture,
together with 83.9 wt. % of DMAC, were poured into a stirring
vessel at a temperature of 60.degree. C. with the stirring rotation
speed of 90 rpm; after they were basically dissolved, 3.2 wt. % of
PEG was added therein; then they were stirred for 10 hours at a
constant temperature of 60.degree. C., the vacuum debubbling was
performed, and they were stood for 12 hours to form the
spray-membrane slurry. The resulting spray-membrane slurry was
extruded through an spinneret by a dry jet-wet spinning method,
then it was passed through a water coagulant to produce a hollow
filtration membrane. The resulting membrane has a retention
molecule weight of 150,000 daltons, and has a pure water filtration
yield of 1160 L/m.sup.2h at a pressure of 0.1 MPa and a water
temperature of 25.degree. C.
* * * * *